Injection molding unit for an injection molding machine

ABSTRACT

In an injection molding unit for an injection molding machine, two electric drives are provided as electromechanical injection unit and electromechanical dosing unit, the axis of which are aligned with the axis of injection. A compact injection molding unit that is easy to assemble and maintain is achieved due to the fact that the first and second electric drives are disposed on the injection bridge on both sides of a separating plane that extends substantially crosswise to the axis of injection and separates the area of influence of the first electric drive from the area of influence of the second electric drive.

FIELD OF THE ART

The invention relates to an injection molding unit for an injectionmolding machine for the processing of plastic materials and otherplasticisable substances . An injection molding unit of this type is forinjecting these substances into a mold which can be fixed on theinjection molding machine, ceramic substances or other powderysubstances being also considered, for example, as the plasticisablesubstances to be injected.

DESCRIPTION OF THE RELATED ART

An injection molding unit of this type, known in EP 0 662 382 B1, hastwo electric drives for the screw drive. One motor is for carrying outthe rotary motion of the screw, that is for dosing the substance, theother motor is for carrying out the axial displacement of the screw. Thetwo electric drives are configured as hollow-shaft motors and aredisposed with their axes in alignment with the axis of the screw andconsequently with the axis of injection. To guarantee the interaction ofthe two motors, they are disposed so as to be displaceable relative toeach other, the members driven by the respective rotor engaging oneanother in a costly manner. Because the two hollow shaft motors nest inone another, they can only be replaced as one unit, which increases bothmanufacturing costs and servicing costs.

EP 0 723 848 A1 makes known an injection molding unit where two electricdrives, configured as hollow-shaft motors, are also used for rotatingthe screw and for displacing the screw in an axial manner. The motorsare disposed in alignment with the axis of injection. To enabledisplacement of the motors relative to each other, a plurality of splineshafts, which mesh with each other, are provided so that it is possibleat any time for either of the motors to displace the feed screw. Thesespline shafts necessitate tate additional expenditure. The hollow-shaftmotors cannot be exchanged independently of one another, at least as faras the rotors of these motors are concerned.

SUMMARY OF THE INVENTION

Proceeding from this related the present invention provides a compactinjection molding unit which is simple in design in view of expenditurefor assembly and maintenance.

The injection molding unit of the present invention includes: a carrierblock for the accommodation of a plasticizing cylinder; a feed screwwhich is disposed in the plasticizing cylinder along an axis ofinjection for the injection of the plasticisable substances into a mold;an injection bridge, which is displaceable axially along the axis ofinjection and on which the feed screw is mounted so as to bedisplaceable via at least one bearing element; an electromechanicalinjection unit for the axial displacement of injection bridge and feedscrew through the intermediary of a linear displacement means driven bya first electric drive, the axis of the first electric drive beingaligned with the axis of injection; and an electromechanical dosing unitfor rotating the feed screw through the intermediary of a secondelectric drive, the axis of the second electric drive being aligned withthe axis of injection. The first and second electric drives are disposedon the injection bridge on both sides of a parting plane which extendssubstantially crosswise to the axis of injection and separates the areaof influence of the first electric drive from the area of influence ofthe second electric drive.

The two electric drives are disposed independently of one another onboth sides of a parting plane so that there is no need for costlyconnection mechanisms. Consequently, components of the individual motorsmust not go beyond their side. Between the electric drives, which areeffective in both directions of the parting plane, a passive space can,consequently, be formed which makes it possible for the two motors to besupported on a common supporting member.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in more detail below by way of the enclosedFigures using an exemplified embodiment. In which:

FIG. 1 is a side view of an injection molding unit supported on amachine base and positioned on a mold.

FIG. 2 is a horizontal section through the injection molding unit at thelevel of the guide braces,

FIG. 3 is an enlarged section from the representation in FIG. 2 in thearea of the injection bridge,

FIG. 4 is another exemplified embodiment of the supporting member in arepresentation as in FIG. 3,

FIG. 5 is a representation as in FIG. 2 in another exemplifiedembodiment,

FIG. 6 is an enlarged section from the representation in FIG. 5 in thearea of the injection bridge.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

The invention is now described in more detail in an exemplary mannerwith reference to the enclosed drawings. The exemplified embodiments,however, are not examples which are meant to restrict the conceptaccording to the invention to a specific physical arrangement.

The injection molding unit represented schematically in FIG. 1 is acomponent part of an injection molding machine and is disposed on themachine base 35 of this injection molding machine. When injecting into amold 13, a part of which can be seen on the left hand side in FIG. 1,the injection molding unit engages an opening 34 a in a stationary moldcarrier 34. The injection molding unit on an injection molding machineis for processing plasticisable substances, essentially for injectingthese substances, e.g. plastic materials, ceramic substances and otherpowdery substances into the cavity of the mold 13.

In accordance with FIG. 1, the injection molding machine has a carrierblock 10 for accommodating a plasticizing cylinder 11. The feed screw12, shown in FIG. 2, is disposed along the axis of injection s—s in theplasticizing cylinder 11 for injecting the plasticisable substances intothe mold 13. An injection bridge 14 is disposed so as to be displaceableaxially in the direction of the axis of injection s—s on braces 31, inthe exemplified embodiment on cylinders 27 disposed on these braces 31.The axis of injection s—s coincides for the most part with the centralaxis of the feed screw 12. The injection bridge 14 is displaced axiallyvia an electromechanical injection unit 16, the linear displacementmeans 16 a of which is rotationally mounted on the injection bridge 14via at least one bearing member 17, 53. The linear displacement means 16a of the injection unit 16 is displaced relative to the axialdisplacement of injection bridge 14 and feed screw 12 through theintermediary of a first electric drive E, the axis of which is inalignment with the axis of injection s—s.

An electromechanical dosing unit 60 is disposed on the side of theinjection bridge 14 located opposite the first electric drive E. Thisdosing unit is rotated with the feed screw 12 during the preparation inthe plasticizing cylinder 11. To this end there is a second electricdrive R, the axis of which is also in alignment with the axis ofinjection s—s.

In accordance with FIG. 2, the first and second electric drives E, R aredisposed on a supporting member 45 of the injection bridge 14. Theinjection bridge 14 itself slides on the cylinders 27 with two identicalsliding parts 14 a per brace 31, between which the supporting member 45is clamped. The braces 31 are supported at the front end of theinjection molding unit via a carrier 39. When the injection bridge 14 isdisplaced, this latter slides along a guide 37.

The electric drives E, R are disposed on the injection bridge 14 on twosides of a parting plane t—t which extends essentially transverse to theaxis of injection s—s and separates the influence area of the firstelectric drive E from the influence area of the other electric drive R.Emanating from the parting plane t—t, the second electric drive Rextends in the direction of the plasticizing cylinder 11, whilst thefirst electric drive E with associated linear displacement means 16 aextends away from the parting plane t—t in the opposite direction. Thefirst electric drive E, therefore, works to the right in the Figures forthe axial displacement of the feed screw 12 with its linear displacementmeans 16 a, although there can also subsequently be an axialdisplacement of the feed screw 12 to the left through the force frame,formed via the supporting member 18, cylinder 27 and carrier block 10.Contrary to this, the second electric drive R works to the left for therotation of the feed screw. There must be no other connection betweenthe motors. A passive space is formed so that the parting plane t—tforms a barrier between the two motors.

In principle, the parting plane t—t will, for the most part, be at rightangles to the axis of injection as shown in the Figures. It is alsopossible for the parting plane t—t to extend essentially cross-wise tothe axis of injection if on the supporting element 45, for example, twofirst electric drives E work to the left and to the right next to theone, for example, second electric drive R of the dosing unit 60 fordisplacing the linear displacement means 16 a. If the two first electricdrives E work together on a supporting member 18, the areas of influenceof the motors are still separated in the Figures to the left and to theright of a parting plane which is then meander-shaped but extendsessentially cross-wise to the axis of injection.

This arrangement for the two electric motors E, R reduces the previouslyhigh expenditure on construction as neither the motors nor the parts ofthe rotors have to be inserted into one another. To generate the axialdisplacement, the linear displacement means 16 a is supported on theforce frame and consequently outside the injection bridge 14 via thesupporting member 18. This can be used for a more sturdy supporting ofthe entire injection molding unit. It is insignificant which motors areused and this is illustrated by the “black box” in FIG. 2, as long asthe motors are suitable for working separately independently of oneanother to both sides of the parting plane t—t. Slow running motors canbe used just as much as the smaller high speed motors with gears whichhave to be actuated more dynamically because of the smaller rotationalmass. Smaller motors also reduce the moments of inertia.

The design of the electric drives E, R is clearly shown in FIG. 3. Theyare extensively similar in construction and are accommodated back toback in recesses 45 a, 45 b in the supporting member 45. The tworecesses 45 a, 45 b are separated from each other by a general centralpart 45 c. The stator 42 or respectively 44 is situated initially at thebottom of the respective recess. The rotor 41 or respectively 43 of theelectric drive is located in the interior of this stator. This rotor ismounted on the supporting member 45 via the bearing member 53 orrespectively 52. Gear teeth 41 a or respectively 43 a are assigned tothe rotors 41 or respectively 43, which gear teeth are connected tointermediate gear teeth 23 or planet pinions. These intermediate gearteeth form a planetary gearing which is integrated in the electric driveor at least in the supporting member 45, such that electric drive andgearing form a structural unit which can be prefabricated at themanufacturer's plant and which has only to be supplied to the supportingmember 45. The intermediate gear teeth 23 mesh with an outer ring gear48. From the intermediate gear teeth, the rotation is transmitted toentrainment means 49, which in the center support an axis of connectionfor the connection of two structurally-similar coupling devices 46, 47.The entrainment means are mounted via bearing members 17 or respectively15 and are retained in the recesses 45 a, 45 b together with all othercomponents by the two lateral parts of the injection bridge 14.

In place of the planetary gearing just referred to above, otherarbitrary gearing can also be used. Where required, a gear can bedispensed with entirely by using a slow running motor.

In FIG. 3 the two electric drives are not only similarly designed butthe two electric drives are also disposed in a mirror symmetricalmanner, even with reference to the coupling devices 46, 47. However,this symmetry and similar design can be dispensed with. The feed screw12 is connected on the one hand on the coupling devices and the lineardisplacement means 16 a on the other hand. This means that, whererequired, it is possible to replace only one of the two electric drivesindependently of the other. Over and above this, the manufacturer willspend a smaller amount on storage holding the corresponding electricdrives for injecting and dosing.

FIG. 2 explains the design of the injection unit 16. The lineardisplacement means 16 a is driven by the first electric drive E asalready described. The linear displacement means 16 a of the injectionunit 16 has a spindlehead 16 c which engages in a member which isconfigured as threaded sleeve 16 b and interacts with the lineardisplacement means 16 a. The threaded sleeve 16 b is fixedly supportedon the supporting member 18. Between spindlehead 16 c and threadedsleeve 16 b are disposed a plurality of planets 16 d interacting withthese latter such that the torque can be further translated here. Thisalso contributes to the retention of identical electric drives E, R. Therod 16 e of the linear displacement means 16 a supports the spindlehead16 c. Coaxially to the axis of the rod 16 e and supported on theinjection bridge 14, there is a pipe 26 which engages in recesses 61between threaded sleeve 16 b and supporting member 18 in every positionof the injection unit 16. In this respect, the supporting member 18forms a pan-like recess 18 a.

Other systems can obviously also be used in place of the lineardisplacement means 16 a described here, such as, for example, spindlesystems, ball spindles or gear racks. The prerequisite condition issolely the generation of linear displacement.

The injection bridge 14 is mounted so as to be axially displaceable onthe cylinders 27 of an hydraulic piston-cylinder unit D. Thepiston-cylinder unit D is for positioning the injection molding unitonto the mold 13. Guide braces 31 simultaneously form the piston rodsfor the cylinders 27 and to this end support a rotary piston 30. Thecarrier block 10 is fixed in the area of the front cylinder cover 32 andthe supporting member 18 in the area of the rear cylinder cover 33.Supporting member 18 and carrier block 10 together with the cylinders 27form the rigid force frame which increases precision. Between carrierblock 10 and supporting member 18, the injection bridge 14 is supportedon the cylinders 27 so as to be axially displaceable but rotational.

During dosing the second electric drive R is driven and rotates the feedscrew 12 as mentioned earlier. As the substance prepared increases and,on account of the feed screw rotating, amasses in front of the feedscrew, the feed screw 12 and consequently the injection bridge 14 ispressed back. To preserve the predetermined dynamic pressure, the axialforce on the feed screw can be increased or reduced by the firstelectric drive E of the injection unit 16 by simultaneously rotating thefeed screw 12 at a freely selectable torque and a freely selectablespeed. To this end the rod 16 e is rotated, generating, via interactionof the parts of the injection unit 16, an axial displacement of thelinear displacement means 16 a, supported on the supporting member 18.This displacement leads to the desired withdrawal of the feed screw 12or respectively injection unit 16. The connected injection is effectedessentially only through the intermediary of the first electric drive Ein the manner just described.

Where required, the pipe 26 can also be used as a power transmissionmember to relieve the rod 16 e or to enable it to be sized in anothermanner. For this, however, a connection (not illustrated in thedrawings) must be created between threaded sleeve 16 b and pressure pipe26, by, for example, the forces being transmitted from the threadedsleeve 16 b to the spindlehead 16 c via the planets 16 d. Thespindlehead could then work on an axial bearing member via a shoulderand transfer the forces to the pipe, which, where necessary, can beeffected in not attending the linear displacement means.

FIG. 4 shows another exemplified embodiment of the supporting member 45.The central part 45 c here is a separate part which braces the outerparts of the injection bridge 14 with the supporting element 45 viasecurement means 62. This means that the rotors 41, 43 are also mountedin another manner in the area of the central part 45 c.

Another essential difference is most certainly the flow of the coolantlubricant indicated. A medium passes into the injection bridge 14 in thedirection of the arrow 63 via the duct 64. From there it passes into thebearing 15, passes through this latter and the duct 65 to the rotor 43until it reaches the passage area 68 between the motors. Past the rotor41 it passes via the duct 69 and the bearing 17 to the duct 70 so as tobe drawn off via the arrow 71. The medium can simultaneously cool thedrives E, R and lubricate the movable parts. There is no need toseparate lubricant and cooling medium where the lubricant (oil) issimultaneously the coolant, which also means that there is no need for aseal between these areas. As a hydraulic medium is provided anyway onthe machine for the cylinders 27, even this hydraulic medium can be usedas lubricant and coolant.

FIGS. 5 and 6 show another exemplified embodiment. The two electricdrives here are cooled hollow-shaft motors. As rotor 43, electric driveR drives a hollow-shaft which is connected to the entrainment means 49to the left in FIG. 6. Via rotor 41, electric drive E drives a hollowshaft 72, configured as a threaded sleeve, in which the lineardisplacement means 16 a engages, which is fixedly supported on thesupporting member 18 and works in a reverse manner relative to FIG. 3.The liquid cooling is effected in the direction of the arrow via thecooling ducts 73,74 which run round the motors externally. The length ofthe hollow-shaft (rotor 43) of the hollow-shaft motor is preferablyadapted to the maximum stroke of the feed screw 12 or corresponds to thesame, thus ensuring that the entire unit can be designed to be morecompact.

It is obvious that this description can be subject to the most variedmodifications, amendments and adaptations which are in the field ofequivalents to the attached claims.

What is claimed is:
 1. An injection molding unit for an injectionmolding machine for the processing of plastic materials and otherplasticisable substances, comprising; a carrier block for theaccommodation of a plasticizing cylinder; a feed screw which is disposedin the plasticizing cylinder along an axis of injection for theinjection of the plasticisable substances into a mold; an injectionbridge, which is displaceable axially along the axis of injection and onwhich the feed screw is mounted so as to be displaceable via at leastone bearing element; an electromechanical injection unit for the axialdisplacement of injection bridge and feed screw through the intermediaryof a linear displacement means driven by a first electric drive, theaxis of the first electric drive being aligned with the axis ofinjection; and an electromechanical dosing unit for rotating the feedscrew through the intermediary of a second electric drive, the axis ofthe second electric drive being aligned with the axis of injection,wherein the fist and second electric drives are disposed on theinjection bridge on both sides of a parting plane which extendssubstantially crosswise to the axis of injection and separates the areaof influence of the first electric drive from the area of influence ofthe second electric drive.
 2. The injection molding unit in accordancewith claim 1, wherein emanating from the parting plane, the secondelectric drive extends in the direction of the plasticizing cylinder,whilst the first electric drive with the associated linear displacementmeans extends away from the parting plane in the opposite direction. 3.The injection molding unit in accordance with claim 1, wherein the firstand second electric drives are disposed on a supporting member of theinjection bridge and that the linear displacement means is supportedoutside the injection bridge on a supporting member.
 4. The injectionmolding unit in accordance with claim 1, wherein the first and secondelectric drives are accommodated back to back in recesses in asupporting member of the injection bridge.
 5. The injection molding unitin accordance with claim 1, wherein the first and second electric drivesare constructed the same.
 6. The injection molding unit in accordancewith claim 1, wherein the first and second electric drives with theassociated planetary gearing form one structural unit.
 7. The injectionmolding unit in accordance with claim 1, wherein the linear displacementmeans of the injection unit, connected to a rotor of the first electricdrive, has a spindlehead which engages a member which is configured as athreaded sleeve and interacts with the linear displacement means, whichmember is fixedly supported on the supporting member.
 8. The injectionmolding unit in accordance with claim 7, wherein between spindlehead andthreaded sleeve a plurality of planets are disposed interacting with theformer.
 9. The injection molding unit in accordance with claim 7,wherein a rod of the linear displacement means supports the spindleheadand co-axially to the axis of the rod is surrounded by a pipe which isfixedly supported on the injection bridge, which pipe engages thesupporting member in each position of the injection unit.
 10. Theinjection molding unit in accordance with claim 1, wherein a hydraulicpiston-cylinder unit is provided for the positioning of the injectionmolding unit to the mold, the cylinders of which are axiallydisplaceable on the stationary piston rods, which are configured asbraces and together with carrier block and supporting member form aframe.
 11. The injection molding unit in accordance with claim 10,wherein the carrier block is secured in the area of the front cylindercover and the supporting member in the area of the rear cylinder cover,and that the injection bridge is axially displaceable between thecarrier block and the supporting member on the cylinders of thepiston-cylinder unit and is supported in a rotational manner.
 12. Theinjection molding unit in accordance with claim 1, wherein at least oneof the first and second electric drives is a hollow-shaft motor.
 13. Theinjection molding unit in accordance with claim 12, wherein the lengthof the hollow shaft corresponds to the maximum stroke of the feed screw.14. An injection molding unit for an injection molding machine for theprocessing of plastic materials and other plasticisable substances,comprising; a carrier block for the accommodation of a plasticizingcylinder; a feed screw which is disposed in the plasticizing cylinderfor the injection of the plasticisable substances into a mold; aninjection bridge on which the feed screw is mounted so as to bedisplaceable; an electromechanical injection unit for the axialdisplacement of the injection bridge and feed screw through theintermediary of a first electric drive; and an electromechanical dosingunit for rotating the feed screw through the intermediary of a secondelectric drive; wherein the fist and second electric drives are disposedon the injection bridge on both sides of a parting plane which separatesthe area of influence of the first electric drive from the area ofinfluence of the second electric drive.